Micro-fluid ejection devices, such as ink jet printers continue to evolve as the technology for ink jet printing continues to improve to provide higher speed, higher quality printers. However, the improvement in speed and quality does not come without a price. The micro-fluid ejection heads are more costly to manufacture because of tighter alignment tolerances.
For example, some conventional micro-fluid ejection heads are made with nozzle members (e.g., nozzle plates) containing flow features. The nozzle plates are then aligned and adhesively attached to a semiconductor substrate. However, minor imperfections in the substrate or nozzle plate components of the ejection head or improper alignment of the parts has a significant impact on the performance of the ejection heads.
One advance in providing improved micro-fluid ejection heads is the use of a photoresist layer applied to a device surface of the semiconductor substrate as a thick film layer. The thick film layer is imaged to provide flow features for the micro-fluid ejection heads. Use of the imaged thick film layer enables more accurate alignment between the flow features and ejection actuators on the device surface of the substrate.
While the use of an imaged photoresist layer improves alignment of the flow features to the ejection actuators, there still exist alignment problems and difficulties associated with a nozzle member attached to the thick film layer and the ability to provide suitable nozzles (e.g., holes) in the nozzle layer after it is attached to the thick film layer. In order for micro-fluid ejection heads to provide precise ejection of fluid droplets, the nozzles in the nozzle layer should have a reentrant profile. There is less flow restriction with reentrant nozzles and thus less energy required to eject fluid droplets. The term “reentrant” is used to refer to side wall profiles of the nozzles, wherein exit diameters of the nozzles are smaller than entrance diameters of the nozzles so that the side walls of the nozzles are not perpendicular to a plane defined by an exit surface of the nozzle member.
Conventional nozzle plates are typically made from metal that is electroformed or a polyimide material that is laser ablated and then adhesively attached to the thick film layer. The formation of exit hole diameters smaller than entrance hole diameters is achieved in conventional nozzle plates by forming the holes from an entrance side of the nozzle plate. However, use of such nozzle plates requires an alignment step to attach the nozzle plate to the thick film layer and to align the nozzles with the flow features in the thick film layer and with the fluid ejector actuators.
In order to eliminate such alignment steps, photoimageable nozzle materials may be applied adjacent (e.g., to) the thick film layer by spin coating or lamination techniques. Such spin coating techniques and lamination techniques are done before the nozzles are formed in the nozzle material. Nozzles must then be formed from an exit side of the nozzle material. Conventional photoimaging and developing techniques do not provide suitable reentrant nozzles. For example, conventional photoimaging and developing techniques cannot readily provide nozzles having wall angles of greater than about 4°. Typically, such conventional techniques provide vertical walled nozzles or nozzles having an exit diameter larger than an entrance diameter. For the purposes of this disclosure the term “diameter” is used for simplicity in describing the dimensions of nozzles. However, the term “diameter is not limited to the dimension of circular holes as the nozzles may have other shapes, such as ellipses, stars, etc.
Accordingly, there is a need for, among other things, improved photoresist or photoimageable materials that may be used as nozzle materials and improved techniques for forming reentrant nozzles in such nozzle materials.
In some of the exemplary embodiments of the present invention, there is provided, for example, improved photoimaged nozzle members for a micro-fluid ejection heads, micro-fluid ejection heads containing such nozzle members, and methods for making the same. In one embodiment, a photoresist nozzle layer is applied adjacent a thick film layer on a substrate having fluid ejector actuators. The photoresist nozzle layer has a plurality of nozzles therein. The nozzles are formed in the nozzle layer from an exit surface of the nozzle layer to an entrance surface of the nozzle layer. The nozzles have a reentrant profile with a wall angle greater than about 4° up to about 30° measured from an axis orthogonal to a plane defined by the exit surface of the nozzle layer.
In another embodiment, there is provided a method for making a micro-fluid ejection head. The method includes applying a negative photoresist nozzle layer adjacent a thick film layer on a substrate having a plurality of micro fluid ejection actuators. The nozzle layer has a thickness ranging from about 10 to about 30 microns. A plurality of nozzles are imaged in the nozzle layer from an exit surface of the nozzle layer to an entrance surface of the nozzle layer using a mask. The imaged nozzle layer is developed to provide nozzles having reentrant profiles with wall angles greater than about 4° up to about 30° measured from an axis orthogonal to a plane defined by the exit surface of the nozzle layer.
An advantage of at least certain of the exemplary embodiments described herein is that nozzles may be made in a photoimageable material from an exit side thereof while still providing nozzles having improved fluid flow characteristics. The terms “exit side” and “exit surface” refer to a side or surface of the nozzle member that is opposite to a surface or side that is attached adjacent to a thick film layer on a substrate. In particular, the compositions and methods described herein may enable the formation of reentrant nozzles in a photoimageable nozzle material after the nozzle material is applied adjacent a thick film layer on a substrate. Hence, alignment problems associated with aligning a nozzle material to fluid ejection actuators and flow features on a substrate can be substantially reduced. Unlike conventional photoimaging methods, the compositions and methods described herein enable the formation of nozzles with wall angles greater than about 4°.
For purposes of the disclosure, “difunctional epoxy” means epoxy compounds and materials having only two epoxy functional groups in the molecule. “Multifunctional epoxy” means epoxy compounds and materials having more than two epoxy functional groups in the molecule.